Method for supplementing digital image with picture element, and digital image encoder and decoder using the same

ABSTRACT

The present invention provides a method of supplementing a digital picture with a shorter delay time and less calculations. The padding method is applied to a picture having a great motion, and results in producing a prediction signal with small errors. The present invention also provides an apparatus using the same method. To be more specific about the method, in a digital picture data including picture information indicating an object, a picture is resolved into a plurality of regions adjoining with each other, and each of the insignificant sample value of a region containing the boundary of the object shape is supplemented (padded) by the values obtained from transforming of the significant pixels near to the insignificant pixels.

FIELD OF THE INVENTION

[0001] The present invention relates to a method of padding a digitalpicture having an arbitrary shape, and an encoder and a decoder ofdigital picture using the same method.

BACKGROUND ART

[0002] It is necessary to compress (encode) a digital picture forpromoting the efficiency of its storage and transmission. Severalmethods of encoding are available as prior arts such as “discrete cosinetransform” (DCT) including JPEG and MPEG, and other wave-form encodingmethods such as “subband”, “wavelet”, “fractal” and the like. Further,in order to remove a redundant signal between pictures, a predictionmethod between pictures is employed, and then the differential signal isencoded by wave-form encoding method.

[0003] According to the recent trend, the object constituting a pictureare individually encoded and transmitted, for improving the codingefficiency as well as allowing reproduction of the individual objectswhich constitute a picture. On a reproducing side, each object isdecoded, and the reproduced objects are composited into the picture fordisplaying. Per-object base encoding method allows the user to combineobjects arbitrarily, whereby a motion picture can be re-edited withease. Further, depending on the congestion of the communication channel,performance of a reproducing apparatus or a user's taste, even a lessimportant object is saved from being reproduced, a motion picture can bestill identified.

[0004] In order to encode a picture having an arbitrary shape (i.e., anobject), an appropriate transformation method adapted to the shape isemployed, such as the “shape adaptive discrete cosine transform”, or aninsignificant region of the picture is padded by a predetermined methodand then a conventional cosine transform (8×8) is provided, where theinsignificant region is an outside of the display region of the object,and contains no pixel data for displaying an object, in other words, theregion consists of insignificant sample values only. On the other hand,insignificant sample values can be found at the object boundary of aprediction region (e.g., a block consisting of 16×16 pixels) which isobtained through a motion compensation of a reference picture reproducedin the past for removing a redundant signal between pictures. This typeof prediction region is firstly padded, then a the difference betweenthe subject region and the predict region is obtained, and then,transformed and encoded. The reason why the prediction region is paddedis to suppress a differential signal.

[0005] When the efficiency of encoding/decoding a digital picture isconsidered, how to pad the insignificant pixels is an important subject,and this influences a decoded picture quality and transmitting dataquantity.

[0006] The prior art discussed above discloses the following steps: Anoverall picture is referenced and padded first, to prevent a predictionregion from including insignificant sample values, then the predictionregion is obtained by a motion compensation or other methods. How to padthe overall picture is, repeating a significant sample value on anobject boundary and replacing an insignificant sample values therewith.When a sample is padded by scanning both horizontal and verticaldirections, an average of both the padded values are taken. Thisconventional method pads the whole picture, and therefore providing aprediction region with less errors for a picture having a great motion.

[0007] However, when the whole image of a reproduced reference pictureis referenced and padded, the reference picture must be entirelydecoded, before padding can be started. When repetitive padding isapplied, the amount of calculation increases in proportion to thepicture size. In other words, this padding method requires a largeamount of processing and a long delay time, and sometimes results invery large amount of calculation, for reproducing a picture.

[0008] In order to avoid calculation proportional to the picture size, areproduced boundary region should be padded on per-region basis. Thismethod can solve the delay time and volumes of calculation. However,since this method pads only the boundary region, the significant regionsare limited within the internal region bounded by the boundary regions,and hence limiting the effect of padding. Therefore, this method cannotproduce a prediction signal having less errors for a motion picture witha great motion.

[0009] Since the method of padding the overall picture results inincreasing data amount, only a small advantage can be expected. In otherwords, an insignificant pixel has no pixel values to be encoded, andwhen significant pixels are encoded together with an insignificantpixel, coding efficiency is lowered. For example, when the significantpixels are all in black, the coding efficiency is lowered ifinsignificant pixels are in white, on the other hand, the codingefficiency is promoted if the insignificant pixels are in black. Assuch, a value of the insignificant pixel does not influence a quality ofa reproduced picture, but influences the coding efficiency, therefore,how to deal with the insignificant pixel value should have beendiscussed with care.

DISCLOSURE OF THE INVENTION

[0010] The present invention aims to, firstly, provide a padding method,through which a prediction signal with less errors can be produced for amotion picture having a great motion, accompanying a short delay timeand a small volume of calculation.

[0011] In order to achieve the above goal, according to the presentinvention, in a digital picture data including picture information whichindicates an object, a picture is resolved into a plurality of regionsadjoining with each other, and insignificant sample value of a regioncontaining the boundary of the object shape is padded by the valuesobtained from transforming the significant pixel values near to theinsignificant pixel values.

[0012] The simplest functional transformation is that an insignificantpixel value is replaced with a significant pixel value adjoiningthereto, and this replacement is just repeated. The combination of thisrepetitive replacement method and the above method can produce the moreeffective padding .

[0013] Further, there is a method of enlarging a padding region to anappropriate extent. This method extends the region to be padded to aninsignificant regions consisting of insignificant pixel values only,where the insignificant regions are near to the regions containing anobject boundary. In addition to padding these insignificant regions,this method also pads the regions containing the object boundary usingvalues obtained by applying a functional transformation to thesignificant pixel values of the region. This method enables processinginvolving larger motion compensation.

[0014] The present invention aims to, secondly, apply the above methodof padding a digital picture to the methods of encoding/decoding digitalpicture and the apparatus thereof, whereby a picture compression processproducing the better picture quality with a small amount of processingdata can be realized.

[0015] In order to achieve the above goal, a picture encoder comprisingthe following elements is prepared: In a digital picture data includingpicture information which indicates an object of the input signal, wherethe input signal comprises (1) a signal indicating a pixel value and (2)a significant signal indicating whether a pixel value of each pixel issignificant or not, the picture encoder comprises,

[0016] (a) predicted picture generation means for producing a predictedpicture signal corresponding to the input signal by using a decodedpicture signal,

[0017] (b) pixel value generation means for resolving the picture into aplurality of regions adjoining to each other, padding the insignificantsample value of the region containing a boundary of the object shapewith a functional-transformed significant pixel values located near tothe above insignificant pixel value,

[0018] (c) subtraction means for subtracting the output of the predictedpicture generation means from an output of the pixel value generationmeans,

[0019] (d) encoding means for encoding the output of the subtractionmeans,

[0020] (e) decoding means for decoding the output of the encoding means,

[0021] (f) adding means for adding an output of the decoding means andthe output of the predicted picture generation means, and

[0022] (g) memory means for storing the output of the adding meanstemporarily for further use in the predicted picture generation means,

[0023] wherein the output of the encoding means is an output of thispicture encoder.

[0024] The corresponding digital picture decoder comprising thefollowing elements is also prepared:

[0025] (a′) decoding means for decoding the input signal,

[0026] (b′) predicted picture generation means for producing a predictedpicture signal corresponding to the input signal by using a decodedpicture signal,

[0027] (c′) pixel value generation means for producing a pixel valuefrom significant pixel value in the predicted picture signal by using apredetermined function, replacing insignificant pixel value of thepredicted picture signal with the produced picture value, and outputtingthe replaced pixel value,

[0028] (d′) adding means for adding an output of the decoding means andan output of the pixel value generation means, and

[0029] (e′) memory means for storing temporarily an output of the addingmeans for further use in the predicted picture generation means, whereinthe output of the decoding means is an output of this picture decoder.

[0030] An insignificant region adjoining to the boundary of object shapeand consisting of insignificant sample values only, is padded, wherebyprocessing region is appropriately enlarged without increasing datavolume remarkably, and as a result, the accuracy of processes includinga motion compensation is promoted.

[0031] To be more specific about the padding method of a digital pictureaccording to the present invention, the method comprising the followingsteps is prepared:

[0032] a first padding process for scanning a picture sample having anarbitrary shape consisting of significant and insignificant samplevalues along a first direction, and in the first direction, producing afirst padded picture by replacing the insignificant sample values withthe significant sample values selected through a predetermined method,

[0033] a second padding process for scanning each sample of the firstpadded picture consisting of significant and insignificant sample valuesalong a second direction, and in the second direction, replacing theinsignificant sample values of the first padded picture with thesignificant sample values selected through a predetermined method or thesample values padded in the first padding process.

[0034] To be more specific about the padding method of a digital pictureaccording to the present invention, another method comprising thefollowing steps is prepared:

[0035] resolving a digital picture having an arbitrary shape into aplurality of regions,

[0036] processing the regions according to a predetermined order,

[0037] padding the insignificant region adjoining to a boundary regionat the shape boundary and consisting of insignificant sample valuesonly, with a predetermined padding values.

[0038] When the subject region is not an insignificant region, inparticular, if a previous region adjoining to a subject region is aninsignificant region at the predetermined order, the previous region ispadded with a padding value found through a predetermined method.

[0039] When the subject region is an insignificant region, inparticular, if a previous region adjoining to a subject region is not aninsignificant region at the predetermined order, the subject region ispadded with a padding value found through a predetermined method.

[0040] A picture encoder employing the method of padding a digitalpicture according to the present invention comprises the followingelements:

[0041] input means for receiving a digital picture data having anarbitrary shape,

[0042] process means for resolving the digital picture into a pluralityof regions adjoining to each other,

[0043] a first adding device for receiving a data of a subject regionand a data of a prediction region, and producing a data of adifferential region,

[0044] an encoding device for receiving the data of the differentialregion, and compressing thereof into a data of a compressed differentialregion through a predetermined method,

[0045] a decoding device for receiving the data of the compressseddifferential region, and decoding thereof into a data of an expandeddifferential region,

[0046] a second adding device for receiving the data of the expandeddifferential region, adding the data of the prediction region thereto,and producing a data of a reproduced region,

[0047] a first padding device for receiving the data of the reproducedregion and padding the insignificant sample values included in thereproduced region through the previously described padding method,

[0048] a frame memory for storing the data of the reproduced region ofwhich insignificant sample value has been padded.

[0049] Instead of or in addition to the first padding device, a secondpadding device is employed for padding insignificant sample valuesincluded in the prediction region.

[0050] A picture decoder employing the method of padding a digitalpicture according to the present invention comprises the followingelements:

[0051] input means for receiving a compressed coded data,

[0052] a data analyzing device for analyzing the compressed coded data,and outputting a compressed differential signal,

[0053] a decoding device for decoding the compressed differential signalinto an expanded differential signal,

[0054] an adding device for adding the expanded differential signal anda prediction signal, producing a reproduced signal and outputtingthereof,

[0055] a first padding device for padding an insignificant sample valuesincluded in the reproduced signal through the previously describedmethod,

[0056] a frame memory for storing a picture data padded by the firstpadding device as the prediction signal.

[0057] Instead of or in addition to the first padding device, a secondpadding device is employed for padding insignificant sample valuesincluded in the prediction region.

BRIEF DESCRIPTION OF THE DRAWINGS

[0058]FIG. 1 is a schematic diagram depicting a padding method of adigital picture in a first exemplary embodiment of the presentinvention.

[0059]FIG. 2 is a schematic diagram depicting a first modification ofthe padding method of the digital picture in the first exemplaryembodiment of the present invention.

[0060]FIG. 3 is a schematic diagram depicting a second modification ofthe padding method of the digital picture in the first exemplaryembodiment of the present invention.

[0061]FIG. 4 is a schematic diagram depicting a third modification ofthe padding method of the digital picture in the first exemplaryembodiment of the present invention.

[0062]FIG. 5 is a schematic diagram depicting a padding method of adigital picture in a second exemplary embodiment of the presentinvention.

[0063]FIG. 6 is a schematic diagram depicting a padding method of adigital picture in a third exemplary embodiment of the presentinvention.

[0064]FIG. 7 is a schematic diagram depicting a first modification ofthe padding method of the digital picture in the third exemplaryembodiment of the present invention.

[0065]FIG. 8 is a schematic diagram depicting a padding method of adigital picture in a fourth exemplary embodiment of the presentinvention.

[0066]FIG. 9 is a schematic diagram depicting a padding method of adigital picture in a fifth exemplary embodiment of the presentinvention.

[0067]FIG. 10 is a schematic diagram depicting a padding method of adigital picture in a sixth exemplary embodiment of the presentinvention.

[0068]FIG. 11 is a schematic diagram depicting a padding method of adigital picture in a seventh exemplary embodiment of the presentinvention.

[0069]FIG. 12 is a schematic diagram depicting a padding method of adigital picture in a eighth exemplary embodiment of the presentinvention.

[0070]FIG. 13 is a schematic diagram depicting a padding method of adigital picture in a ninth exemplary embodiment of the presentinvention.

[0071]FIG. 14 is a schematic diagram depicting a first modification ofthe padding method of the digital picture in the seventh exemplaryembodiment of the present invention.

[0072]FIG. 15 is a schematic diagram depicting a padding method of adigital picture in a ninth exemplary embodiment of the presentinvention.

[0073]FIG. 16 is a schematic diagram depicting a first modification ofthe padding method of the digital picture in the ninth exemplaryembodiment of the present invention.

[0074]FIG. 17 is a schematic diagram depicting a padding method of adigital picture in a tenth exemplary embodiment of the presentinvention.

[0075]FIG. 18 is a schematic diagram depicting a first modification ofthe padding method of the digital picture in the tenth exemplaryembodiment of the present invention.

[0076]FIG. 19 is a flow chart depicting a padding method of a digitalpicture in a 11^(th) exemplary embodiment of the present invention.

[0077]FIG. 20 is a schematic diagram depicting an embodiment of a methodof padding a region, which is employed in the padding method of thedigital picture in the 11^(th) exemplary embodiment of the presentinvention, where (A) shows an example; a padding value is an average ofsignificant pixel values arranged along the horizontal direction, (B)shows an example; a padding value is repeated significant pixel valuesarranged along the horizontal direction, and (C) shows another example;a padding value is repeated significant pixel values arranged along thehorizontal direction.

[0078]FIG. 21 is a schematic diagram depicting an embodiment of a methodof padding a region, which is employed in the padding method of thedigital picture in the 12^(th) exemplary embodiment of the presentinvention, where (A) shows an example; a padding value is an average ofsignificant pixel values arranged along the vertical direction, (B)shows an example; a padding value is repeated significant pixel valuesarranged along the vertical direction, and (C) shows another example; apadding value is repeated significant pixel values arranged along thevertical direction.

[0079]FIG. 22 is a flow chart depicting a padding method of a digitalpicture in a 13^(th) exemplary embodiment of the present invention.

[0080]FIG. 23 is a flow chart depicting a second modification of thepadding method of the digital picture in a 14^(th) exemplary embodimentof the present invention.

[0081]FIG. 24 is a schematic diagram of a first example of the picturepadded through the padding method of the digital picture in the 14^(th)exemplary embodiment of the present invention.

[0082]FIG. 25 is a schematic diagram of a second example of the picturepadded through the padding method of the digital picture in the 14^(th)exemplary embodiment of the present invention.

[0083]FIG. 26 is a schematic diagram of a third example of the picturepadded through the padding method of the digital picture in the 14^(th)exemplary embodiment of the present invention.

[0084]FIG. 27 is a block diagram depicting a digital picture encoderutilized in a 15^(th) exemplary embodiment of the present invention.

[0085]FIG. 28 is a block diagram depicting a modification of the digitalpicture encoder utilized in the 15^(th) exemplary embodiment of thepresent invention.

[0086]FIG. 29 is a block diagram depicting a digital picture decoderutilized in a 16^(th) exemplary embodiment of the present invention.

[0087]FIG. 30 is a block diagram depicting a digital picture encoderutilized in a 17^(th) exemplary embodiment of the present invention.

[0088]FIG. 31 is a block diagram depicting a digital picture decoderutilized in a 18^(th) exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0089] The present invention is detailed hereinafter by referring toexemplary embodiments.

[0090] (Exemplary Embodiment 1)

[0091]FIG. 1 is a schematic diagram depicting a padding method of adigital picture in a first exemplary embodiment of the presentinvention. A picture 501 is a subject picture to be padded. Each latticein the picture 501 represents a pixel i.e., a sample from the picture.Pixels 502-507 are significant samples, and other samples areinsignificant.

[0092] In this embodiment, a shape signal of the picture is referred tofor determining whether a sample is significant or insignificant. Whenthe shape signal is “0”, the sample is insignificant, and when the shapesignal is “1”, the sample is significant.

[0093] When a picture 508 is produced from the picture 501, eachinsignificant sample is padded as described below:

[0094] First, scan each line of the picture 501. In this scanningprocess, when a significant sample is detected, a value thereof issubstituted to an insignificant sample, e.g., when the first line isscanned, padding process is not done because of no significant sample,and when the second line is scanned, samples 509, 510 and 511 areinsignificant, while a sample 502 is significant, thus the insignificantsamples are padded with a value “a” of the sample 502. In other words,the value of sample 502 is repeatedly padded to the adjoininginsignificant samples 511, 510 and 509 sequentially. In the same manner,a value “b” of sample 503 is repeatedly padded to samples 512, 513 and514.

[0095] The third line is padded as same as the second line, and thefourth line is not padded because of no significant sample. In thepicture 508 thus padded, the second and third lines have significantvalues.

[0096] Next, based on the picture 508, the remaining insignificantsamples are padded. As shown in picture 519, scan the picture invertical direction, and pad insignificant samples 520 and 528respectively with the samples 509 and 515 which have been padded in thepicture 508. As such, samples 521-527 and 529-535 are padded in the samemanner.

[0097] Through the above steps, the insignificant samples can be paddedin a simple manner while the continuity between the samples ismaintained, and therefore, improves the calculation efficiency includingcompression of pictures, while a picture quality is maintained.

[0098] In this embodiment, padding is performed through scanning alongthe horizontal and vertical directions which are perpendicular to eachother; however, the scanning along a slanted line produces also the sameeffect. Further, a method of vertical scanning first, followed byhorizontal scanning also produces the same effect. As long as thecontinuity of the samples is maintained, methods other than padding aninsignificant sample with the nearest significant sample are applicable.

[0099]FIG. 2 is a schematic diagram depicting a first modification ofthe padding method of the digital picture in the first exemplaryembodiment of the present invention. In the picture 508, when ahorizontal scanning is performed, mirroring can be done with respect tothe boundary as a center between the insignificant and significantsamples. For example, samples 511 and 502 are the boundary in a mirror,and a value of sample 502 is substituted into a value of sample 511,then a value of sample 503 is substitute into a sample 510. As such, thepicture 501 is sequentially padded along the arrow mark, to the picture508, and then to the picture 519, until all insignificant samples arepadded.

[0100]FIG. 3 is a schematic diagram depicting a second modification ofthe padding method of the digital picture in the first exemplaryembodiment of the present invention. This method is applied when aninsignificant sample is located between significant samples. A case ofhorizontal scanning is detailed here, however, the details can beapplied in the case of scanning other directions: Samples 612 and 613are padded with a value of a sample 602. Another method is that samples611 and 614 can be padded with a value of sample 607. The first methodis that samples are scanned from left to right by extending asignificant sample as it is for padding. The second method is thatsamples are scanned from right to left by extending the significantsample as it is for padding. The third method is that an insignificantsample is padded with its nearest sample along the scanning direction.Samples 615 and 618 are padded by this method. Lastly, an insignificantsample is padded with an average value of significant samples on bothsides of the insignificant sample. Samples 616 and 617 are padded bythis method.

[0101]FIG. 4 is a schematic diagram depicting a third modification ofthe padding method of the digital picture in the first exemplaryembodiment of the present invention. When a picture indicates an ovalobject, i.e., significant samples gather so that they shape into anoval, and this picture is basically padded by the method used in FIG. 1.

[0102] A picture 701 comprises collected significant samples 702. First,as shown in a picture 703, insignificant samples are padded byhorizontal scanning, next, as shown in a picture 704, insignificantsamples are padded by using significant samples or the samples padded inthe picture 703 through vertical scanning. On the other hand, as shownin a picture 705, insignificant samples are padded by vertical scanningfirst, and then by horizontal scanning. An average of the pictures 704and 706 thus padded is taken, whereby a picture 707 is produced. Thispadding method can maintain sequence between the significant samples andthe padded samples even in a more complex picture, and thus can dealwith calculations efficiently while maintaining a picture quality.

[0103] (Exemplary Embodiment 2)

[0104]FIG. 5 is a schematic diagram depicting a padding method of adigital picture in a second exemplary embodiment of the presentinvention.

[0105] A picture 801 comprises collected significant samples 802. First,scan the picture 801 horizontally, and substitute significant samplevalues into the nearest insignificant samples to produce a picture 803.At the same time, scan the picture 801 vertically, and substitutesignificant samples into the nearest insignificant samples to produce apicture 804.

[0106] An average of the pictures 803 and 804 is taken to produce apicture 806. An average of the collected significant samples 802 wouldresult in the same value, thus the averaging is not needed.

[0107] Since there are some samples values double padded in the picture803 and 804, an average of both the padded values is taken. If there isonly one padded value available, this value becomes the padded value ofthe picture 806. In the padding process of the pictures 803 and 804, asample having no padding value remains as an insignificant sample as itis. This insignificant sample is then to be padded with a value of thenearest significant sample or padded sample. When more than one paddingvalues are available, an average of these values, or one of them is usedfor padding. All samples are finally padded as shown in a picture 811.

[0108] This embodiment shows an another padding method to maintaincontinuity between the collected significant samples and insignificantsamples both forming a complex shape, like the exemplary embodiment 1.

[0109] (Exemplary Embodiment 3)

[0110]FIG. 6 is a schematic diagram depicting a padding method of adigital picture in a third exemplary embodiment of the presentinvention.

[0111] A picture 901 comprises collected significant samples 902. Inthis embodiment, a region 904 surrounding the collected significantsamples 902 is determined and an insignificant sample is padded withinthe region 904. The same padding method detailed above is utilized alsoin this embodiment. A remaining region 905 is padded through a simplemethod by referring to the padded region 904, thus all insignificantsamples are padded (Ref. to FIG. 906.)

[0112] The region 904 is preferably rectangular; however, it may beanother shape. The region 904 may be the smallest rectangular whichincludes the collected significant samples 902, or a rectangular afterextending the smallest rectangular by “k” samples. The value “k” isdetermined so that a size of the rectangular can satisfy a predeterminedcondition, e.g., “k” is determined so that the size of the rectangularcan be a multiple of 16.

[0113]FIG. 7 is a schematic diagram depicting one modification of thepadding method of the digital picture in the third exemplary embodimentof the present invention, and a picture 910 comprises collectedsignificant samples 911, 912 and 913. The picture 910 is resolved intorespective regions 915, 916 and 917 which include the above collectedsignificant samples, and then the respective regions are padded throughthe method previously described.

[0114] (Exemplary Embodiment 4)

[0115]FIG. 8 is a schematic diagram depicting a padding method of adigital picture in a fourth exemplary embodiment of the presentinvention.

[0116] A picture 920 is resolved into blocks each of which consists ofM×N samples, and then are padded. Preferably M=N=8 or 16, or anotherarbitrary value is acceptable, or the picture can be resolved intotriangles or another shape. Blocks 921 through 929 include partiallysignificant samples, and insignificant samples thereof are paddedthrough the method previously described by referring to the values ofthe significant samples.

[0117] When blocks 930 and 931, which do not contain significantsamples, are padded, a predetermined value (preferably “128”) is usedfor padding, or the nearest sample value is referred for padding. Theblock 930 is taken as an example; the block 930 is nearest to a block929 among the blocks having significant samples. This is obtained byfinding a distance between the coordinates points in the upper leftcorners of respective blocks. Then an average of significant samples inthe block 929 is taken to be used for padding.

[0118] In the case of the block 931, the nearest block which hassignificant samples is a block 922, therefore, an average of thesignificant samples can be taken for padding; however, samples 934, 935,936 and 937 in boundary can be repeated for padding.

[0119] As such, padding block by block in the predetermined procedurecan realize more efficient calculation process.

[0120] Various exemplary embodiments are available as follows when themethod of padding a digital picture according to the present inventionis applied to a picture encoder and decoder.

[0121] (Exemplary Embodiment 5)

[0122]FIG. 9 is a schematic diagram depicting a digital picture encoderin a fifth exemplary embodiment of the present invention. FIG. 9 liststhe following elements: an input terminal 201, a first adder 202, anencoder 203, a discrete cosine transformer (DCT) 204, a quantizer 205,an output terminal 206, a decoder 207, an inverse quantizer 208, aninverse discrete cosine transformer 209, a second adder 210, variablelength encoder (VLC) 211, a frame memory 213, a motion estimator 214, amotion compensator 215, a first padder 240, and a second padder 241.

[0123] An operation of the digital picture encoder comprising the aboveelements is detailed hereinafter. First, input a picture having anarbitrary shape into the input terminal 201. Second, resolve the pictureinto a plurality of regions adjoining each other. In this embodiment,the picture is resolved into blocks each of which consists of 8×8, or16×16 samples; however, an any other shapes can be acceptable. Then,input subject blocks to be encoded into the motion estimator 214 via aline 225. At the same time, input a previously reproduced picture(hereinafter called a reference picture) stored in a frame memory 213into the motion estimator 214, and then, output a motion displacementinformation (hereinafter called a motion vector) which gives theprediction signal having the least error with respect to the subjectblock through the block-matching method or other methods. Third, sendthis motion vector to the motion compensator 215, where a predictionblock is produced from the reference picture. The motion vector is sentto the VLC 211 via a line 228, and is converted into a variable lengthsignal.

[0124] The subject block is sent to the first padder 240, where theblock is padded through the method previously mentioned to produce apadding subject block. A prediction block is sent to the second padder241, where the block is padded through the method previously mentionedto produce a padding prediction block.

[0125] The padding subject block and padding prediction block are sentto the first adder 202, where a difference between the two blocks isfound to produce a differential block, which is compressed by theencoder 203, namely by the DCT 204 and quantizer 205, in this exemplaryembodiment. The quantized data is sent to the VLC 211, where the data isconverted into a variable length code, which is fed together with otherside information including motion vectors into the output terminal 206.

[0126] On the other hand, the compressed data is sent to the decoder207, where the data is expanded, namely, the compressed data undergoesthe inverse quantizer 208 and is expanded into a data in spatial domainby IDCT 209. The expanded data of the differential block is added to apadding prediction block data which is sent via line 227 to produce areproduced block. The data of the reproduced block is stored in theframe memory 213. To indicate whether a sample value is significant orinsignificant, a corresponding shape signal, encoded and subsequentlydecoded, is used as reference, although this is not shown in thedrawings.

[0127] As such, a subject block and a prediction block are padded,whereby a large predicted error, which is caused by a shift of an edgepart because of a motion compensation, can be suppressed.

[0128] This is not shown in the drawings; however, the padder 246 can beplaced before the motion compensator 215. In this embodiment, DCT isadopted; however, a shape adaptive DCT, subband or wavelet can beadopted instead.

[0129] (Exemplary Embodiment 6)

[0130]FIG. 10 is a schematic diagram depicting a digital picture encoderin a sixth exemplary embodiment of the present invention. The sixthexemplary embodiment has basically the same operation as that of thefifth exemplary embodiment. The different point is at the first adder240, a value for padding the prediction block is used for padding thesubject block. This value is transmitted from the second padder 241 viaa line 243 to the first padder 240. Sharing the padding value as suchmakes almost all the differential values “0” (zero), whereby theprediction error is further suppressed.

[0131] (Exemplary Embodiment 7)

[0132]FIG. 11 is a schematic diagram depicting a digital picture decoderin a seventh exemplary embodiment of the present invention. FIG. 11lists the following elements: input terminal 301, data analyzer (parser)302, inverse quantizer 304, IDCT 305, adder 306, output terminal 307,frame memory 309, motion compensator 310 and a padder 330.

[0133] An operation of the digital picture decoder comprising the aboveelements is detailed hereinafter. First, input a compressed data intothe input terminal 301, then analyze the data by the data analyzer 302,second, output the data of the compressed differential block to thedecoder 303 via a line 312, third, output a motion vector to the motioncompensator 310 via a line 318. In the decoder 303, expand thecompressed differential block to restore thereof to a expandeddifferential block, namely, in this embodiment, the compresseddifferential block undergoes the inverse quantizer 304 and IDCT 305,where a signal in the frequency domain is transformed into a signal inthe spatial domain. Then, input the motion vector via a line 318 intothe motion compensator 310, where an address for accessing the framememory 309 is produced based on the motion vector, and a predictionblock is produced using the picture to be stored in the frame memory309. Then, transmit the prediction block into the padder 330, whereinsignificant samples are padded through the method previously detailed,and thereby producing a padding prediction block. Next, input thepadding prediction block and the expanded differential block into theadder 306 to add both the block, thereby producing a reproduced block.Finally, output the reproduced block to the output terminal 307, and atthe same time, store the reproduced block into the frame memory 309.

[0134] The above embodiment describes that the prediction blockundergone the motion compensation is padded; however, the block can bepadded during the motion compensation, which includes overlapped motioncompensation. To indicate whether a sample value is significant orinsignificant, a decoded shape signal should be referred, although thisis not shown in the drawings. FIG. 14 is a schematic diagram depicting afirst modification of the padding method of the digital picture in theseventh exemplary embodiment of the present invention, and has basicallythe same operation shown in FIG. 11. In this embodiment, the padder 332is placed before the motion compensator 310.

[0135] (Exemplary Embodiment 8)

[0136]FIG. 12 is a schematic diagram depicting a digital picture encoderin an eighth exemplary embodiment of the present invention. The basicoperation is the same as shown in FIG. 9. The padder 212 is placedbefore the frame memory, whereby a reproduced block tapped off from theadder 210 can be advantageously padded immediately. Further the padder244 is placed before DCT 204. The padder 244 pads the blocks so that DCTcoefficients becomes smaller. Regarding the differential block, inparticular, insignificant regions of the subject blocks are padded with“0” (zero).

[0137]FIG. 13 is a schematic diagram depicting a padding method of adigital picture in a ninth exemplary embodiment of the presentinvention. The padder 246 is placed after the motion compensator 215,which is an additional element to those in FIG. 12. After the motioncompensation, the predicted signal is further padded in order to give aneffectiveness of suppressing the prediction errors. This is not shown inthe drawings, however, the padder 246 can be placed before the motioncompensator 215.

[0138] (Exemplary Embodiment 9)

[0139]FIG. 15 is a schematic diagram depicting a digital picture decoderin a ninth exemplary embodiment of the present invention. This decodercorresponds to the decoder depicted in FIG. 12. The operation of thisdecoder is basically the same as that in FIG. 14. In this embodiment, apadder 308 is placed before the frame memory 309, whereby a reproducedblock can be padded immediately and then stored in the frame memory 309.

[0140]FIG. 16 is a schematic diagram depicting a first modification ofthe decoder of the digital picture in the ninth exemplary embodiment ofthe present invention. This decoder corresponds to that in FIG. 13. Theoperation of the decoder is basically the same as that in FIG. 15. Onlythe different point is that a padder 330 is placed after the motioncompensator 310 in order to pad the predicted block.

[0141] (Exemplary Embodiment 10)

[0142]FIG. 17 is a schematic diagram depicting a padding method employedin an encoder/decoder of a digital picture in a tenth exemplaryembodiment of the present invention. The operation of the padder 330 isdescribed hereinafter using FIG. 11 as an example. In FIG. 17, a subjectblock comprises collected significant samples 943 and collectedinsignificant samples 944. A portion hatched by oblique lines representssignificant regions. A predicted block 941 is obtained through a motioncompensation, and comprises collected significant samples and collectedinsignificant samples.

[0143] In the decoder shown in FIG. 11, a predicted block 941 is paddedand then sent to the adder 306. In the padder 330, the entireinsignificant region (of the predicted block) 946 can be padded;however, it preferable to pad the insignificant region of the predictedblock covered by the significant region of the subject block because ofthe less calculation volumes. By referring to the shape of the subjectblock 940, both the significant and insignificant regions are determined(region 947 of the block 942), and then only the region 947 is padded byreferring to itself.

[0144]FIG. 18 is a schematic diagram depicting a modification of thepadding method employed in a digital picture encoder/decoder in thetenth exemplary embodiment of the present invention. Assume that nosignificant samples exist in a subject block of padding, and the padder308 shown in FIG. 15 is used as an example. Assume that a block 962 ofFIG. 18 is the subject block of padding, and since no significantsamples exist in this block, the block cannot be padded within the blockby referring to itself.

[0145] In order to overcome the above problem, find an adjacent blockcomprising at least one significant sample, and pad the subject block byreferring to the adjacent block. The padder in FIG. 15; however,reproduces the block 962 in advance of the block 964, thus it isimpossible to pad the block by referring to the block 964. Then, searchthe reproduced blocks 966, 965, 961 and 963 sequentially for a firstblock which contains significant samples, and pad the block by referringto the found block.

[0146] In the case that the predicted block undergone the motioncompensation does not have a significant sample, a subject block ispadded in the same manner, i.e., through referring to the reproducedblocks having a significant sample and being adjacent to the subjectblock. A method of calculating a padding value can be an averagingmethod or a repetitive padding method.

[0147] The above embodiments prove that the picture encoder and decoderof the present invention can encode insignificant pixels, which do notinfluence a picture quality, by making the pixels such values asincreasing the coding efficiency, whereby the coding efficiency ispromoted, thus the encoder and decoder of the present invention have agreat advantage in practical uses.

[0148] (Exemplary Embodiment 11)

[0149]FIG. 19 is a flow chart depicting a padding method of a digitalpicture in an 11^(th) exemplary embodiment of the present invention.First, input a picture having an arbitrary shape, second resolve thepicture into regions adjacent with each other, third, scan each regionaccording to a predetermined order, and finally, process each region oneby one according to the flow chart shown in FIG. 19. In this embodiment,start scanning from the upper left and follow the same order as theraster scanning. The scanned region can be a triangle, rectangle orsquare. In this embodiment, the picture is resolved into squares each ofwhich consisting of N×N samples, where N=8 or 16. The square of N×Nsamples is called a block hereinafter.

[0150] On Step 12, determine whether a subject block is entirely outsidean object (picture having an arbitrary shape) or not. When the subjectblock is entirely outside the object, every sample of the subject blockis not significant sample. In this embodiment, to determine whether asample value is significant or not, the shape signal of the respectivepicture is referred. When the shape signal is “0”, the sample value isinsignificant. When the shape signal is “1”, the sample value issignificant.

[0151] When the subject block is not entirely outside the object,advance to Step 14. Then determine whether previous blocks adjacent tothe subject block are entirely outside the object or not, where theprevious block is the block already processed according to the scanningorder. When the adjacent previous blocks are entirely outside theobject, on Step 16, a padding value is calculated according to apredetermined method. On Step 18, the sample values of the previousblocks adjacent to the subject block is substituted with the paddingvalue so that the sample values are padded.

[0152] On Step 12, when the subject block is entirely outside theobject, advance to Step 20. Then determine whether the previous blocksadjacent to the subject block is entirely outside the object or not.When the previous blocks are not entirely outside the object, a paddingvalue is calculated according to the predetermined method on Step 22 ,and the sample values of the subject block are substituted with thepadding value on Step 24 so that the sample values are padded. When theadjacent previous blocks are padded on Step 18, the previous blocks canbe taken as not to be entirely outside of the object on Step 20. Repeatthis process until the last block is processed (Steps 26 and 28.)

[0153] (Exemplary Embodiment 12)

[0154]FIGS. 20 and 21 are schematic diagram depicting calculationmethods of padding values. FIG. 20 shows a case where a present block isadjacent to a previous block in a horizontal direction. In FIG. 20(A), ablock 132 is a present block and a block 130 is a previous block. Eachlattice represents a sample (pixel) of the picture. Assume that a block130 is entirely outside an object, and take an average of the values ofsignificant samples, 134, 136, 138, 140, 142 and 144, then substitutethe average value for each sample (lattice) in the previous block forpadding. In FIG. 20(B), pad each sample (lattice) of the previous block146, which is entirely outside the object, by repeating values ofsignificant samples 150, 152, 154, 156 of the present block 148. Inother words, each lattice on the first, second, third and fourth linesof the previous block 146 is substituted with the values of samples 150,152, 154, and 156. In FIG. 20(C), the present block 160 is entirelyoutside the object and the previous block 158 is not outside the object.In this case, each lattice of the present block 160 is padded byrepeating values of significant samples 162, 164, 166 and 168 of theprevious block 158.

[0155]FIG. 21 depicts the case where the present block is adjacent tothe previous block in a vertical direction. In FIG. 21(A), a block 172is the present block and a block 170 is the previous block. Each latticerepresents a sample (pixel) of the picture. Assume that a block 170 isentirely outside the object, and take an average of the values ofsignificant samples 174, 176, 178, 180, 182 and 184 which are containedin the present block 172, then substitute the average value for eachsample (lattice) in the previous block 170 for padding. In FIG. 21(B),pad each sample (lattice) of the previous block 186, which is entirelyoutside the object, by repeating values of significant samples 190, 192,194, 196. In other words, each lattice on the first, second, third andfourth rows of the previous block 186 is substituted with the values ofsamples 196, 194, 192, and 190. In FIG. 20(C), the present block 160 isentirely outside the object and the previous block 158 is not outsidethe object. In this case, each lattice of the present block 198 ispadded by repeating values of significant samples 1100, 1102, 1104, 1106of the previous block 199. This embodiment details a block of ×4 formaking the long story short, but the same description can be applied toa block of N×N (N:arbitrary integer.)

[0156] (Exemplary Embodiment 13)

[0157] In FIG. 22, Step 13 is added to the flow chart shown in FIG. 19.In other words, when a present block is not entirely outside an object,the region contained in the present block and outside the object ispadded through Step 13 and thereafter. The present block 132 of FIG.20(A) is an example of a block containing regions outside the object.Samples 134, 136, 138, 140 142 and 144 are significant and within theobject. The other samples (the lattices not painted) are insignificantand outside the object.

[0158] A method of padding these insignificant samples is to substitutethe average of significant samples therefor. In this embodiment, thesamples 134, 136 and 144 at boundary are repeated in the horizontal andvertical directions for padding. When two padding values are available,an average thereof is used for padding. Due to the padding of thepresent block through Step 13, all the samples of the present block aresubstituted with a unique value, therefore, the previous block can bepadded on Step 18 by repeating the values of significant samples of thepresent block existing at the boundary between the present and previousblocks, as shown in FIG. 20(B) or FIG. 21(B). An average of thesignificant samples can be used instead of repeating the sample values.

[0159] (Exemplary Embodiment 14)

[0160]FIG. 23 is a flow chart depicting the processes where the previousblock adjacent to the present block in horizontal direction is utilizedon Step 15, 19 and 21 shown in FIG. 22. FIG. 24 shows a picture 108which is an example padded through the process shown in FIG. 23. A starshape 110 is a significant object, and the other part consists ofinsignificant samples. The picture 108 is resolved into blocks of 7×7. Ablock having the same texture as the block 1114 is padded through Step19 or Step 24 shown in FIG. 23.

[0161] The padding method of this embodiment is described by referringto FIGS. 23 and 24. First, the block 1112 is discussed. Since thepresent block 1112 is not entirely outside the object on Step 12, thepresent block is padded through Step 13. On Step 15, the previous blockadjacent to the present block is not entirely outside the object, thusno padding is provided.

[0162] Next, the block 1114 is discussed. Since the present block 1114is entirely outside the object, the process is advanced to Step 21,where the previous block adjacent to in the horizontal direction is notentirely outside the object, thus the present block 1114 is padded byreferring thereto on Step 24.

[0163] Finally, the block 1116 is discussed. Since the present block1116 is entirely outside the object on Step 12, the process is advancedto Step 21, where the previous block 1115 is not entirely outside theobject, thus the present block 1116 is padded by referring thereto onStep 24.

[0164] When the block 1117 is processed, the present block 1117 is notentirely outside the object on Step 12, thus the block is padded on Step13. On Step 15, the previous block 116 adjacent to in horizontaldirection is entirely outside the object, the previous block is paddedon Step 19. In other words, the block 1116 is padded twice. When aplurality of padding values are available, an average of these valuesare taken, or one of these values can be selected for padding. Thepicture 108 is thus padded through expanding thereof in the horizontaldirection.

[0165] When the horizontal direction is changed to vertical direction inthe processes on Steps 15, 19 and 21, a picture undergone the paddingthrough vertical expansion as shown in FIG. 25 is obtained. When bothblocks adjacent to in horizontal and vertical directions are processedin combination, a picture which is padded through extension in bothhorizontal and vertical directions as shown in FIG. 26 can be obtained.In this case, when a sample is padded twice or more, an average of allthe padding values or a part of them are taken. When a plurality ofpadding candidates are available, the nearest candidate in the processorder can be used.

[0166] A picture encoder and decoder which employ the padding methodaccording to the present invention is described hereinafter.

[0167] (Exemplary Embodiment 15)

[0168]FIG. 27 depicts a digital picture encoder used in the 15^(th)exemplary embodiment. FIG. 27 lists the following elements: inputterminal 201, first adder 202, encoder 203, discrete cosine transformer(DCT) 204, quantizer 205, output terminal 206, decoder 207, inversequantizer 208, inverse DCT 209, second adder 210, variable lengthencoder (VLC) 211, padder 212, frame memory 213, motion estimator 214and motion compensator 215.

[0169] An operation of the digital picture encoder comprising the aboveelements is described hereinafter. First, input a picture having anarbitrary shape into the input terminal 201, then resolve the pictureinto a plurality of regions adjacent with each other. In thisembodiment, the block is resolved in to 8×8 blocks or 16×16 blocks;however, the blocks can be resolved into arbitrary shapes.

[0170]FIG. 24 should be referred. Input a subject block of padding intothe motion estimator 214 via a line 225. At the same time, input apreviously reproduced picture (called “reference picture”) stored in theframe memory 213 into the motion estimator.

[0171] Send this motion vector to the motion compensator 215, where apredicted block is produced from the reference picture. Send this motionvector also to the VLC 211 via a line 228, where the vector is convertedinto a variable length code. Then, send the subject block and predictedblock to the first adder 202, where a differential block is produced byusing the difference therebetween. Next, compress the differential blockin the encoder 203. In this embodiment, the differential block iscompressed in the DCT 204 and the quantizer 205.

[0172] On the other hand, send the compressed data to the decoder 207and expand it. In this embodiment, inversely quantize the compresseddata in the inverse quantizer 208, and then expand thereof into the datain spatial domain in the IDCT 209. Add the predicted block sent via aline 227 to the expanded differential block to produce a reproducedblock. Then, input the reproduced block to the padder 212, whereinsignificant samples of the reproduced block are substituted forpadding through the padding method described in the ₁₁th exemplaryembodiment. Then, store the padded reproduced block in the frame memory213. Refer to the shape signal already encoded or decoded when a samplevalue should be indicated as significant or insignificant (this is notdescribed in the drawings though.)

[0173] The padded picture to be stored in the frame memory 213 is, e.g.,shown in FIGS. 24, 25 or 26. Send the padded picture via a line 224 tothe motion estimator 214 and the motion compensator 215. In thisembodiment, an active area of the motion estimator and motioncompensator is limited within the padded region (the painted regions inFIGS. 24, 25 and 26), in other words, samples outsides the padded regionare not accessed.

[0174]FIG. 28 depicts the picture encoder having a recorder 229 coupledto the picture encoder shown in FIG. 27. The data converted to avariable length code by the VLC 211 is stored into a magnetic medium(tape or disc) or an optical disc via the recorder 229.

[0175] As such, the region adjacent to the object boundary is padded,whereby the active area of the motion estimation and motion compensationcan be enlarged. Thus, the predicted block with less remainingdifference can be obtained for the picture having a great motion.Further, the padding method according to the present invention cansuppress the delay time and calculation volumes.

[0176] The discrete cosine transform is employed in this embodiment;however, the shape adaptive discrete cosine transform, subband, orwavelet can also produce the same effect.

[0177] (Exemplary Embodiment 16)

[0178]FIG. 29 depicts a digital picture encoder used in the 16^(th)exemplary embodiment. FIG. 29 lists the following elements: inputterminal 301, data analyzer 302, decoder 303, inverse quantizer 304,IDCT (inverse discrete cosine transformer) 305, adder 306, outputterminal 307, padder 308, frame memory 309 and padder 310.

[0179] An operation of the digital picture decoder comprising the aboveelements is described hereinafter. First, input a compressed data to theinput terminal 301, then analyze the data in the data analyzer 302.Output the data of the compressed differential block to the decoder 303via a line 312. Next, output a motion vector to the motion compensator310 via a line 318. In the decoder 303, expand the compressed remainingblock and restore it to a expanded differential block. In thisembodiment, the compressed differential block undergoes the inversequantizer 304 and IDCT 305 to be transformed from a signal in frequencydomian into a signal in a spatial domain. Then input the motion vectorto the motion compensator 310 via a line 318.

[0180] In the motion compensator 310, produce an address based on themotion vector in order to access the frame memory 309, and also producea predicted block using a picture stored in the frame memory 309. Then,input the produced predicted block and the expanded differential blockto the adder 306 to produce a reproduced block. Output the reproducedblock to the output terminal 307, and at the same time, input thereof tothe padder 308. Finally, pad the reproduced block through the paddingmethod detailed in the 11^(th) exemplary embodiment, and store thepadded block in the frame memory 309.

[0181] (Exemplary Embodiment 17)

[0182]FIG. 30 depicts a digital picture encoder used in the 17^(th)exemplary embodiment. The basic structure is the same as shown in FIG.27. An initializer 230 is used instead of the padder 212. Before apicture is stored in the frame memory 213, the frame memory 213 pictureis initialized with a predetermined initialization value by theinitializer 230. The reproduced block tapped off from the second padder210 is stored in the frame memory 213. The initialization value can be afixed value, or an average value of significant samples of reproducedpicture in the past.

[0183]FIG. 31 depicts the picture encoder having the recorder 229coupled to the picture encoder shown in FIG. 30. The data converted to avariable length code by the VLC 211 is stored into a magnetic medium(tape or disc) or an optical disc via the recorder 229.

[0184] (Exemplary Embodiment 18)

[0185]FIG. 32 depicts a digital picture decoder used in the 18^(th)exemplary embodiment. It has basically the same structure as that inFIG. 29, and employs an initializer 320 instead of the padder 308.Before a picture is stored in a frame memory 309, the frame memory isinitialized with a predetermined initialization value by the initializer320. The reproduced block tapped off from a padder 306 is stored in theframe memory 309. The initialization value can be a fixed value, or anaverage value of significant samples of reproduced picture in the past.

[0186] Industrial Applicability

[0187] The present invention provides a simple padding method, throughwhich a small region undergone a motion compensation or a smallreproduced region are padded, whereby calculation volumes can besubstantially reduced. Since a subject region of padding is a closedsmall region, it takes a shorter delay time than when padding isperformed across the entire picture. Further, not only a boundary regionbut also a region adjacent thereto, which comprises insignificantsamples only is padded, and a motion is estimated as well as motion iscompensated using the padded regions, whereby a predicted signal withless difference can be obtained. These factors contribute to the higherefficiency of encoding/decoding a picture having an arbitrary shape.

1. In digital picture data including picture information which indicatesan object, a method of padding a digital picture comprising the stepsof: (a) resolving said picture into a plurality of regions adjacent witheach other, (b) padding an insignificant pixel value in a regionincluding a boundary of a shape of said object with a significant pixelvalue near insignificant pixels values, said significant pixel valueundergone a functional transformation.
 2. The method of padding adigital picture as defined in claim 1 , wherein the insignificant pixelvalue to be padded adjoins said significant pixel value.
 3. The methodof padding a digital picture as defined in claim 1 , wherein aninsignificant region near the region including a boundary of the shapeof the object, said insignificant region comprising of an insignificantpixel value, is padded with a significant pixel value in the regionincluding said boundary of the shape of said object, said significantpixel value undergone the functional transformation.
 4. A pictureencoder comprising: (a) predicted picture production means for receivinga picture signal as an input signal including a significant signal whichidentifies a pixel value of each pixel as one of a significant pixel andan insignificant pixel, and producing a predicted picture signalcorresponding to said input signal using a picture signal alreadydecoded, (b) pixel value production means for padding the insignificantpixel of said picture signal with a pixel value produced from asignificant pixel value near the insignificant pixel by using apredetermined function, and outputting the padded pixel, (c) deductionmeans for deducting an output of said predicted picture production meansfrom an output of said pixel value production means, (d) encoding meansfor encoding an output of said deduction means, (e) decoding means fordecoding an output of said encoding means, (f) adding means for addingan output of said decoding means to the output of said predicted pictureproduction means, (g) memory means for storing temporarily an output ofsaid adding means for being used in said predicted picture productionmeans, wherein said picture encoder taps off the output of said encodingmeans.
 5. The picture encoder as defined in claim 4 wherein the pixelvalue production means pads an insignificant region comprising of aninsignificant pixel value, said region adjacent to a boundary of a shapeof an object.
 6. A digital picture decoder comprising: (a) decodingmeans for decoding an input signal, (b) predicted picture productionmeans producing a predicted picture signal corresponding to said inputsignal using a picture signal already decoded, (c) pixel valueproduction means for producing a pixel value from a significant pixelvalue of said predicted picture signal by using a predeterminedfunction, padding an insignificant pixel value of said predicted picturesignal with said pixel value and outputting the padded pixel, (d) addingmeans for adding an output of said decoding means to the output of saidpixel value production means, (e) memory means for storing temporarilyan output of said adding means for being used in said predicted pictureproduction means, wherein said picture decoder taps off the output ofsaid adding means.
 7. The digital picture decoder as defined in claim 6, wherein the pixel value production means pads an insignificant regioncomprising an insignificant pixel value, said region adjacent to aboundary of a shape of an object.
 8. A method of picture paddingcomprising a first padding process and a second padding process, whereinthe first padding process comprises the steps of: (a) scanning a pixelof a picture having an arbitrary shape comprising significant andinsignificant pixels along a first direction, (b) in the firstdirection, producing a first padded picture by padding an insignificantpixel value with a significant pixel value selected through apredetermined method, and the second padding process comprises the stepsof: (c) scanning each pixel of said first padded picture comprising thesignificant pixel and the insignificant pixels along a second direction,(d) in the second direction, padding the insignificant pixel with thesignificant pixel values selected through the predetermined method orthe pixel value padded in the first padding process.
 9. A method ofpicture padding comprising a first padding process and a second paddingprocess, wherein the first padding process comprises the steps of: (a)scanning a pixel of a picture having an arbitrary shape comprisingsignificant and insignificant pixels along a first direction, (b) in thefirst direction, producing the first padded picture by padding aninsignificant pixel value with a significant pixel value nearest to theinsignificant pixel, and the second padding process comprises the stepsof: (c) scanning each pixel of said first padded picture comprising thesignificant pixel and the insignificant pixel along a second direction,(d) in the second direction, padding the insignificant pixel with thesignificant pixel values nearest to the insignificant pixels or thepixel value padded in the first padding process.
 10. The method ofpicture padding as defined in claim 8 or 9 , wherein said seconddirection is perpendicular to said first direction.
 11. A method ofpicture padding comprising a first, second, third and fourth paddingprocesses, wherein the first padding process comprises the steps of: (a)scanning a pixel of a picture having an arbitrary shape comprisingsignificant and insignificant pixels along a first direction, (b) in thefirst direction, producing a first padded picture by padding aninsignificant pixel value with a significant pixel value selectedthrough a predetermined method, the second padding process comprises thesteps of: (c) scanning each pixel of said first padded picturecomprising the significant pixel and the insignificant pixel along asecond direction, (d) in the second direction, padding the insignificantpixel value of said first padded picture with the significant pixelvalue selected through the predetermined method or with the pixel valuepadded in the first padding process, and producing a second paddedpicture, the third padding process comprises the steps of: (e) scanningthe pixel of said picture having an arbitrary shape comprisingsignificant and insignificant pixels along a third direction, (f) in thethird direction, producing a third padded picture by padding aninsignificant pixel value with a significant pixel value selectedthrough said predetermined method, and the fourth padding processcomprises the steps of: (g) scanning each pixel of said third paddedpicture along a fourth direction, (h) in the fourth direction, paddingan insignificant pixel value with a significant pixel value selectedthrough the predetermined method or the pixel value padded in the thirdpadding process, and producing a fourth padded picture, and (i) takingan average of said second padded picture and said fourth padded picture.12. A method of picture padding comprising a first, second and thirdpadding processes, wherein the first padding process comprises the stepsof: (a) scanning a pixel of a picture having an arbitrary shapecomprising significant and insignificant pixels along a first direction,(b) in the first direction, producing a first padded picture by paddingan insignificant pixel value with a significant pixel value selectedthrough a predetermined method, the second padding process comprises thesteps of: (c) scanning each pixel of said first padded picture along asecond direction, (d) in the second direction, padding an insignificantpixel value with a significant pixel value, and producing a secondpadded picture, (e) taking an average of said first and second paddedpictures, and producing a third padded picture, wherein when both thefirst and second padded pictures have one of a significant pixel valueand a padded pixel value, an average of these values is used for paddingthe third padded picture, and when one of the first and second paddedpicture has a significant pixel value, the significant pixel value isused for padding the third padded picture, and when both the first andsecond padded pictures have no significant pixel value, a pixel value ofthe third padded picture is used for padding an insignificant pixelvalue, and the third padding process comprises the steps of: (f) takingan average value of the significant pixels around the insignificantpixels, and (g) padding the insignificant pixels with said averagevalue.
 13. A method of picture padding comprising the steps of: (a)resolving a picture having an arbitrary shape comprising N (N=1, 2, 3,
 4. . . ) pieces of aggregates having discrete significant pixels into Npieces of regions surrounding said N pieces of aggregates, and (b)padding an insignificant pixel value with a padding value producedthrough a predetermined method using said significant pixel surrounded.14. A method of picture padding comprising the steps of: (a) resolving apicture having an arbitrary shape into a plurality of regions, (b)producing a padding value through a predetermined method using asignificant pixel in a subject region which includes at least oneinsignificant pixel, (c) padding the insignificant pixel of said subjectregion with said padding value.
 15. A method of picture paddingcomprising the steps of: (a) resolving a picture having an arbitraryshape into a plurality of regions, (b) padding a subject region whichincludes no significant pixel with a predetermined padding value.
 16. Adigital picture encoder comprising: input means, first padder, predictedpicture producer, second padder, first adder, encoding means, decodingmeans, second adder and frame memory, wherein a picture having anarbitrary shape is fed into said input means, an insignificant pixelcontained in said picture having an arbitrary shape is padded by thefirst padder with a padding value determined through a first method, apadded input picture is produced, a predicted picture is produced usingsaid frame memory by said predicted picture producer, insignificantpixels of said predicted picture is padded by the second padder with apadding value produced through a second method to produce a paddedpredicted picture, the padded picture and the padded predicted pictureare fed into the first adder, where a differential picture is produced,the differential picture is fed into said encoding means to becompressed into a compressed differential picture through apredetermined method, the compressed differential picture is fed intothe decoding means, where the compressed differential picture isrestored to an expanded differential picture, which is fed into saidsecond adder, where said padded predicted picture is added to theexpanded differential picture to produce a reproduced region, and thereproduced region is stored in the frame memory.
 17. A digital pictureencoder comprising: input means, a first padder, predicted pictureproducer, second padder, first adder, encoding means, decoding means,second adder, and a frame memory, wherein a picture having an arbitraryshape is fed into said input means, a predicted picture is producedusing said frame memory by said predicted picture producer, aninsignificant pixel contained in said predicted picture is padded by thefirst padder with a padding value obtained through a predeterminedmethod, a padded predicted picture is produced, an insignificant pixelof said picture having an arbitrary shape is padded by the second padderwith a padding value obtained through the predetermined method toproduce a padded input picture, the padded picture and the paddedpredicted picture are fed into the first adder, where a differentialpicture is produced, the differential picture is fed into said encodingmeans to be compressed into a compressed differential picture through apredetermined method, the compressed differential picture is fed intothe decoding means, where the compressed differential picture isrestored to an expanded differential picture, which is fed into saidsecond adder, where said padded predicted picture is added to theexpanded differential picture to produce a reproduced region, and thereproduced region is stored in the frame memory.
 18. A digital picturedecoder comprising: input means, a data analyzer, decoding means, adder,predicted picture producer, padder and a frame memory, wherein acompressed data is fed into the input means, the compressed data isanalyzed by the data analyzer to output a compressed differentialsignal, said compressed differential signal is restored to a expandeddifferential signal by said decoding means, a predicted signal isobtained from said frame memory by the predicted picture producer, aninsignificant pixel value contained in the predicted signal is paddedthrough a predetermined method and a padded predicted signal is producedby the padder, the expanded differential signal is added to the paddedpredicted signal by the adder to produce and output an reproducedsignal, at the same time, and the reproduced signal is stored in theframe memory.
 19. A digital picture encoder comprising: input means, afirst adder, encoding means, decoding means, second adder, padder andframe memory, wherein a picture having an arbitrary shape is fed intothe input means, the picture having an arbitrary shape and a predictedpicture stored in the frame memory are fed into the first adder, where adifferential picture is produced, the differential picture is fed intothe encoding means, where the differential picture is compressed to acompressed differential picture through a predetermined method, thecompressed differential picture is fed into the decoding means andrestored to an expanded differential picture through a predeterminedmethod, the expanded differential picture is fed into the second adder,where the predicted picture is added to produce a reproduced picture,the reproduced picture is fed into the padder to pad an insignificantpixel value contained in the reproduced picture through a predeterminedmethod, and the padded reproduced picture is stored in the frame memory.20. A digital picture decoder comprising: input means, a data analyzer,decoding means, adder, padder and frame memory, wherein a compresseddata is fed into the input means, the compressed data is analyzed by thedata analyzer to output a compressed differential signal, which isrestored to a expanded differential signal by said decoding means, theexpanded differential signal and a predicted signal stored in the framememory are added by the adder to produce a reproduced signal, at thesame time, an insignificant pixel value contained in the reproducedsignal is padded by the padder, and the padded reproduced signal isstored in the frame memory.
 21. A digital picture decoder comprising:input means, a data analyzer, decoding means, adder, predicted pictureproducer, first padder, second padder and frame memory, wherein acompressed data is fed into the input means, the compressed data isanalyzed by the data analyzer to output a compressed differentialsignal, said compressed differential signal is restored to a expandeddifferential signal by said decoding means, a predicted signal isobtained from said frame memory by the predicted picture producer, aninsignificant pixel value contained in the predicted signal is paddedthrough a first method by the first padder to produce a padded predictedsignal, the expanded differential signal and the padded predicted signalare added by the adder to produce a reproduced signal, at the same time,an insignificant pixel value contained in the reproduced signal ispadded through a second method by the second padder, and the paddedreproduced signal is stored in the frame memory.
 22. In decoding adigital picture, a method of padding a digital picture comprising thesteps of: (a) inputting a subject picture having a first object, (b)producing a predicted picture having a second object, (c) padding thepredicted picture through changing a scope to be padded in aninsignificant region of the predicted picture depending on the object inthe first picture.
 23. The method of padding a digital picture asdefined in claim 22 wherein a scope to be padded of the insignificantregion of the predicted picture is formed by overlapping aninsignificant region of the second picture and a significant region ofthe first picture.
 24. A digital picture decoder comprising: inputmeans, a data analyzer, decoding means, adder, predicted pictureproducer, padder and a frame memory, wherein a compressed data is fedinto the input means, the compressed data is analyzed by the dataanalyzer to output a compressed differential signal, which is restoredto a expanded differential signal by said decoding means, a predictedsignal is obtained from said frame memory by the predicted pictureproducer, an insignificant pixel value contained in the predicted signalis padded through a predetermined method and a padded predicted signalis produced by the padder, the expanded differential signal is added tothe padded predicted signal by the adder to produce and output areproduced signal, at the same time, the reproduced signal is stored inthe frame memory, wherein said padder restricts a scope to be padded ofthe predicted signal within a region having a significant pixel of thereproduced signal.
 25. A digital picture decoder comprising: inputmeans, a data analyzer, decoding means, adder, predicted pictureproducer, padder and a frame memory, wherein compressed data is fed intothe input means, the compressed data is analyzed by the data analyzer tooutput a compressed differential signal, said compressed differentialsignal is restored to a expanded differential signal by said decodingmeans, a predicted signal is obtained from said frame memory by thepredicted picture producer, an insignificant pixel value contained inthe predicted signal is padded through a predetermined method and apadded predicted signal is produced by the padder, the expandeddifferential signal is added to the padded predicted signal by the adderto produce and output a reproduced signal, at the same time, thereproduced signal is stored in the frame memory, wherein when all thepixels contained in the predicted signal are insignificant pixels, theinsignificant pixels are padded with significant pixels adjacent to thepredicted signal through a predetermined method.
 26. A digital picturedecoder comprising: input means, a data analyzer, decoding means, adder,padder and frame memory, wherein compressed data is fed into the inputmeans, the compressed data is analyzed by the data analyzer to output acompressed differential signal, said compressed differential signal isrestored to an expanded differential signal by said decoding means, theexpanded differential signal and a predicted signal stored in the framememory are added by the adder to produce a reproduced signal, at thesame time, an insignificant pixel value contained in the reproducedsignal is padded by the padder, and the padded reproduced signal isstored in the frame memory, wherein when all the pixels contained in thereproduced signal are insignificant pixels, the insignificant pixels arepadded with significant pixels adjacent to the reproduced signal througha predetermined method.
 27. A method of padding a digital picturecomprising the steps of: (a) resolving a digital picture having anarbitrary shape into a plurality of regions, (b) processing saidplurality of regions according to a predetermined order, (c) padding aninsignificant region comprising of an insignificant pixel and beingadjacent to a boundary region located at a boundary of the shape with apadding value obtained through a predetermined method.
 28. A method ofpadding a digital picture comprising the steps of: (a) resolving adigital picture having an arbitrary shape into a plurality of regions,(b) processing said plurality of regions according to a predeterminedorder, (c) padding an insignificant region comprising of aninsignificant pixel and being adjacent to a boundary region located at aboundary of the shape with a padding value obtained through apredetermined function using a significant pixel of said boundaryregion.
 29. A method of padding a digital picture comprising the stepsof: (a) resolving a digital picture having an arbitrary shape into aplurality of regions, (b) processing said plurality of regions accordingto a predetermined order, (c) padding an insignificant pixel of aboundary region located at a boundary of the shape with a first paddingvalue obtained by a first function, (d) padding an insignificant regioncomprising of an insignificant pixel and being adjacent to said boundaryregion with a second padding value obtained from a second function usingthe padded pixel of said boundary region.
 30. The method of padding adigital picture as defined in claim 27 , 28 or 29, wherein theinsignificant region comprising of an insignificant pixel and beingadjacent to the boundary region in a horizontal direction is padded. 31.The method of padding a digital picture as defined in claim 27 , 28 or29, wherein the insignificant region comprising of an insignificantpixel and being adjacent to the boundary region in a vertical directionis padded.
 32. The method of padding a digital picture as defined inclaim 27 , 28 or 29, wherein when a plurality of padding values areavailable, an average thereof is used for padding.
 33. A method ofpadding a digital picture comprising the steps of: (a) resolving adigital picture having an arbitrary shape into a plurality of regions,(b) processing said plurality of regions according to a pre-determinedorder, (c) padding an insignificant region comprising of aninsignificant pixel and being adjacent to a boundary region located at aboundary of the shape with padding values obtained through apredetermined method, wherein when a subject region is not aninsignificant region and a previous region adjacent to the subjectregion on the predetermined order is an insignificant region, theprevious region is padded with a padding value obtained through apredetermined method, and wherein when the subject region is aninsignificant region and the previous region adjacent to the subjectregion on the predetermined order is not an insignificant region, thesubject region is padded with a padding value obtained through apredetermined method.
 34. A method of padding a digital picturecomprising the steps of: (a) resolving a digital picture having anarbitrary shape into a plurality of regions, (b) processing saidplurality of regions according to a pre-determined order, (c) padding aninsignificant region comprising of an insignificant pixel and beingadjacent to a boundary region located at a boundary of the shape withpadding values obtained through a predetermined method, wherein when asubject region is not an insignificant region and a previous regionadjacent to the subject region on the predetermined order is aninsignificant region, the previous region is padded with a padding valueobtained by a predetermined function using a significant pixel of thesubject region, and wherein when the subject region is an insignificantregion and the previous region adjacent to the subject region on thepredetermined order is not an insignificant region, the subject regionis padded with a padding value obtained by a predetermined functionusing a significant pixel of the previous region.
 35. A method ofpadding a digital picture comprising the steps of: (a) resolving adigital picture having an arbitrary shape into a plurality of regions,(b) processing said plurality of regions according to a pre-determinedorder, (c) padding an insignificant region comprising of aninsignificant pixel and being adjacent to a boundary region located at aboundary of the shape with a padding value obtained through apredetermined method, wherein when a subject region is not aninsignificant region, an insignificant pixel contained in said subjectregion is substituted with a padding value obtained by a first function,and when a previous region adjacent to the subject region on thepredetermined order is an insignificant region, the previous region ispadded with a padding value obtained by a second function using asignificant pixel of the previous region, and wherein when the subjectregion is an insignificant region, the previous region adjacent to thesubject region on the predetermined order, the subject region is paddedwith an padding value obtained from a second function using the pixel ofthe previous region.
 36. The method of padding a digital picture asdefined in claim 33 , 34 or 35, wherein the insignificant regioncomprising of an insignificant pixel and being adjacent to the boundaryregion in a horizontal direction is padded.
 37. The method of padding adigital picture as defined in claim 33 , 34 or 35, wherein theinsignificant region comprising of an insignificant pixel and beingadjacent to the boundary region in a vertical direction is padded. 38.The method of padding a digital picture as defined in claim 33 , 34 or35, wherein when a plurality of padding values are available, an averagethereof is used for padding.
 39. A digital picture decoder comprising:input means, a first adder, encoding means, decoding means, a secondadder, padder and a frame memory, wherein a digital picture having anarbitrary shape is fed into the input means, said digital picture isresolved into a plurality of regions adjacent with each other, theplurality of regions are processed as subject regions according to apredetermined order, said subject regions and a predicted region storedin the frame memory are fed into the first adder, where a differentialregion is produced, the differential region is fed into the encodingmeans, the differential region is compressed into a compresseddifferential region through a predetermined method, the compresseddifferential region is fed into the decoding means to restore thereof toan expanded differential region through a predetermined method, theexpanded differential region is fed into the second adder, where saidpredicted region is added for producing a reproduced region, thereproduced region is fed into the padder to pad an insignificant pixelcontained in the reproduced region through a predetermined method, and apadded reproduced region is stored in the frame memory, wherein saidpadder employs the method of padding as defined in claim 27 , 28 , 29,33, 34, or
 35. 40. A digital picture decoder comprising: input means, adata analyzer, decoding means, adder, padder and frame memory, whereincompressed data is fed into the input means, the compressed data isanalyzed by the data analyzer to output a compressed differentialsignal, said compressed differential signal is restored to a expandeddifferential signal by said decoding means, the expanded differentialsignal and a predicted signal stored in the frame memory are added bythe adder for producing a reproduced signal, at the same time, aninsignificant pixel value included in the reproduced signal is padded bythe padder, and the padded reproduced signal is stored in the framememory, wherein said padder employs the method of padding as defined inclaim 27 , 28 , 29, 33, 34 or
 35. 41. A digital picture decodercomprising: input means, a first adder, encoding means, decoding means,a second adder and a frame memory, wherein a digital picture having anarbitrary shape is fed into the input means, said digital picture isresolved into a plurality of regions adjacent with each other, theplurality of regions are processed as subject regions according to apredetermined order, said subject regions and a predicted region storedin the frame memory are fed into the first adder, where a differentialregion is produced, the differential region is fed into the encodingmeans, the differential region is compressed into a compresseddifferential region through a predetermined method, the compresseddifferential region is fed into the decoding means to restore thereof toan expanded differential region through a predetermined method, theexpanded differential region is fed into the second adder, where saidpredicted region is added for producing a reproduced region, said framememory is initialized by a predetermined initializing value, and thereproduced region is stored in, the initialized frame memory throughoverwriting.
 42. The digital picture encoder as defined in claim 41 ,wherein the predetermined initializing value is an average ofsignificant pixels of a previous picture on an encoding order.
 43. Adigital picture decoder comprising: input means, a data analyzer,decoding means, adder, and frame memory, wherein a compressed data isfed into the input means, the compressed data is analyzed by the dataanalyzer to output a compressed differential signal, said compresseddifferential signal is restored to an expanded differential signal bysaid decoding means, the expanded differential signal and a predictedsignal stored in the frame memory are added by the adder for producing areproduced signal, at the same time, said frame memory is initialized bya predetermined initializing value, the reproduced region is stored inthe initialized frame memory through overwriting.
 44. The digitalpicture decoder as defined in claim 43 , wherein the predeterminedinitializing value is an average of significant pixels of a previouspicture on a decoding order.